SA Node Physiology and Function

The video explains how the heart can beat independently due to pacemaker tissues, focusing on the SA node. It details the SA node's location, structure, and the ion movements that control its rhythmicity. The phases of action potential in the SA node are discussed, highlighting the roles of Na, Ca, and K ions. The video concludes with a summary of the SA node's function as the heart's pacemaker.

Which of the following tissues is the primary pacemaker of the heart?

• Ventricular myocytes

• AV node

• Purkinje fibers

• SA node

Where is the SA node located?

• Left atrium near the pulmonary veins

• Left ventricle near the aorta

• Right ventricle near the tricuspid valve

• Right atrium near the superior vena cava

What is the resting membrane potential of the SA node?

• -40 mV

• -50 mV

• -60 mV

• -70 mV

Which ion's slow entry is referred to as the 'funny current' in the SA node?

• Chloride (Cl)

• Sodium (Na)

• Potassium (K)

• Calcium (Ca)

What happens during phase 0 of the SA node action potential?

• Rapid influx of Na

• Rapid influx of Ca

• Plateau phase

• Efflux of K

Why are phases 1 and 2 absent in the SA node action potential?

• They are only present in ventricular myocytes

• They are only present in atrial myocytes

• They are only present in AV node

• They are only present in Purkinje fibers

What is the effect of K efflux during the action potential in the SA node?

• It causes hyperpolarization

• It causes depolarization

• It causes a plateau phase

• It causes rapid repolarization

What is the term for the SA node's ability to generate its own impulses?

• Automaticity

• Excitability

• Contractility

• Conductivity

Which ions are primarily responsible for the rhythmicity of the SA node?

• Na, K, and Cl

• Ca, K, and Cl

• Na, Ca, and K

• Na, Ca, and Cl

What happens when the SA node's impulse rate is slower than other pacemaker tissues?

• The AV node takes over as the pacemaker

• The fastest tissue becomes the pacemaker

• The Purkinje fibers take over as the pacemaker

• The heart stops beating